1. Field of the Invention
The present invention relates to a Co-base alloy that can be used in overlay welding to form hard beads having high resistance to wear and weld cracks.
2. Description of the Prior Art
In the manufacture of pumps and valves, those parts which are required to have high wear resistance are joined together by overlay welding of a hardfacing alloy. Typical alloys conventionally used for this purpose are a Co-base alloy consisting essentially of 2% Ni, 30% Cr, 12% W, 2% Fe, 2.5% C, with the balance being Co, and a Co-base alloy consisting essentially of 2.5% Ni, 28% Cr, 4% W, 4% Mo, 2% Fe, 1.0% C, with the balance being Co, the percentage being on a weight basis. However, during welding operations, microfissures often develop in a bead due to B, P and S elements that are contained in the alloy as incidental impurities, and the manufacturer tacitly accepts the cracks because the weld bead has one great advantage, high wear resistance. Recently, a proposal has been made that these hard Co-base alloys with their high wear resistance be used as a weld metal in the overlay welding of parts of nuclear power generators, and when they are used for this purpose, the slightest crack is fatal and must be avoided by all means.